We will concentrate on the following aspects: 1) studies of translational misreading in S. cerevisiae; we will characterize the antibiotic resistant mutants genetically and biochemically. In addition we will try to isolate ram (ribosome ambiguity) mutants in yeast. 2) As a means to isolating ribosomal protein genes we will continue work on yeast species characterization and the preparation and analysis of hybrid strains. We will commence studies in which yeast genes will be recombined into bacteriophage DNA and used to infect bacteria. We will identify those plaques that contain r-protein genes by the use of radioimmune assay methods. Once r-protein genes have been found we will study their expression and also use the DNA as a probe to try to identify their chromosome location. 3) Studies of low-level antibiotic resistant mutants will continue with mapping, in vitro translation and ribosomal protein analyzes. We will concentrate on apramycin, fortimycin, and streptomycin.